I really need some help here, I'm just about out of ideas. I have a 1999 Polaris Scrambler 400 4X4 that I've owned from new and it gets relatively light use with no major issues. Recently, when riding, it all of the sudden losses power in low RPMs when in water or trying to climb a hill. almost like the choke is on. On dry land or once you get the RPMs up it will run like a scolded dog. here's what I've done so far:


1. I've rebuilt the carb twice and had Polaris do it once
2. rebuilt both the primary and secondary clutches (completely)
3. tried disconnecting the rev-limiter
4. did a compression test and its at 130 PSI


Any thoughts?

 

A few things come to mind. You could be splashing water on the electronics or the plug cap or plug. Even a small break in the coil wire can cause shorting to ground if water hits it and cause missing. Another is the engine to clutch seal on the clutch backing plate. If it seeps water can cause problems or even the clutch air intake rubber sleeves may need to be looked at for any damage.Plus not a bad idea to remove the recoil starter and clean this area up and seal the recoil housing and rope handle with some good rtv sealant if you play in water a lot.Plus on the 400s check the air box neck. Bad about cracking and can suck water and dirt right into the engine.

 

I'm not sure its necessarily water related because it will do it on dry land with a moderate to seep incline. It's more like when you add a load to it, it bogs. In water, the water is like a couple of inches deep and you can't get it ramp up, so it not like water is getting up in the motor or being splashed on it.


A few more notes
1. the air intake and related part were replaced do to dry rot when trying to take it apart to get carb out.
2. I check the clutch rubber sleeve is tight and crack free

 

Bogging under a load or incline still sounds like it's carb or clutch related. Especially when on flat land once the rpms rise it's able to pick up and run good. You can try dropping the slide needle,make sure the float is parallel with the carb body and check how many turns out the air screw is. Normally around 2 turns but you might want to open it up to allow more air.

 

I currently have a polaris 400 scrambler I was wanting to swap engines with my 350L trailboss they're both 2 stroke engines is there any reason it wouldnt work and whould I only have to swap the engine?

 

As long as you're swapping complete engines. The ignition timing is a little different on the 350 versus the 400 but don't see why you couldn't use the existing 400 electronics for the 350. 99 model shows to use an exciter coil same as the 350. Only way I'd try something like this is if the 400 engine is trashed beyond repair.Dropping from a 99 400 to a 93 model 350 or earlier.